IL-23 is a pro-inflammatory member of the IL-12 cytokine family and plays a pivotal role in the pathogenesis of immune-mediated inflammatory diseases, including psoriatic disease (psoriasis [PsO] and psoriatic arthritis [PsA]) and inflammatory bowel disease (IBD; Crohn’s disease [CD] and ulcerative colitis [UC]) (1–5). This evidence concerns the gene IL23A and psoriasis.